The present invention relates to a footwear construction for preventing knee and hip osteoarthritis, and more particularly, to a footwear construction that reduces knee and hip torques.
Osteoarthritis, sometimes referred to as degenerative or wear-and-tear arthritis, is a common problem that affects joints, particularly the knee and hip joints. Osteoarthritis typically develops with age. The main problem in osteoarthritis is degeneration of the articular cartilage that covers the joint, which progresses slowly over time. This results in areas of the joint where bone rubs against bone. Nearly every person develops some degree of osteoarthritic changes in both the knees and hips in later adulthood.
Knee osteoarthritis in particular accounts for more disability with respect to mobility than any other disease in the elderly. Knee osteoarthritis typically occurs in two areas: on the medial aspect of the knee, and between the patella and femur. During walking (and other weight bearing activities), there is an external varus knee torque throughout the stance period, imparting a compressive force across the medial aspect of the knee. Also, during walking there is a sagittal knee flexor torque during the early to midstance phases that is proportional to the work of the quadriceps muscles which, in turn, is proportional to the strain through the patella tendon and the pressure across the patellofemoral joint.
Other than avoiding acute joint trauma and maintaining normal body weight, there are no proven measures to reduce wear and tear, thereby preventing the development of knee or hip osteoarthritis. Footwear or shoes often include material in the soles that presumably absorb shock, however, they have not been demonstrated to actually reduce joint forces or torques during walking or other weight bearing activities. Shoe designs and arch supports often support the natural arch of the foot, however, they affect only the anatomy of the foot and do not reduce (and in fact can increase) torques about the knees and hips.
Not only are there limited known measures to prevent osteoarthritis, there are limited known measures available for treating or reducing the progression of knee or hip osteoarthritis. Special shoe inserts or orthotics are sometimes used to help relieve pressure and pain. One common type of orthotic used to treat medial knee osteoarthritis has been a lateral heel or sole insert, which has been shown to reduce knee varus torque.
While this wedge-like insert to a regular shoe could be acceptable as a treatment modality for a person with knee osteoarthritis, the shoe insert alone is unlikely to be an acceptable preventative device that could be useful to a healthy person in preventing knee osteoarthritis. In use, such a shoe insert will tend to pronate the foot and collapse the natural arch. Such a tendency toward collapse of the foot arch with repetitive steps is likely to be uncomfortable for healthy people and athletes, and probably does not warrant the risk of foot injuries and deformities. Moreover, the tendency of a foot arch to collapse over time would ultimately increase rather than decrease the knee varus torque.
Thus, there is a need for footwear designs that consistently reduce the external knee varus torque and potentially also reduce the external knee flexor torque and hip torques, without interfering with the natural arch of the foot. Such footwear designs would be particularly useful for prevention of knee and hip osteoarthritis.
The present invention relates to a joint protective shoe construction for preventing as well as treating knee and hip osteoarthritis. The shoe and/or shoe components of the invention, by virtue of the biomechanical design in relation to the foot and lower extremity, reduces the forces through the knee and hip joints during ground contact with the foot. Thus, the shoe does not merely support the foot or reduce shock through the body, but alters the toques and forces proximal to the foot and ankle at the knee and hip. This shoe construction is appropriate for all types of footwear as it reduces the risk of lower extremity osteoarthritis over a lifetime.
More particularly, the invention provides a footwear construction that reduces the external varus torque about the knee. The footwear construction is further believed to reduce the external knee flexor and hip adductor and flexor torques. By reducing joint torques during weight bearing activities, the invention effectively reduces wear and tear of the knee joint and possibly the hip joint as well, thereby preventing or delaying knee and possibly hip osteoarthritis. The invention also, by reducing joint torques, would improve efficiency and performance of walking, running and other weight bearing activities including athletic endeavors. The present invention may also help relieve pain and pressure associated with knee and hip osteoarthritis, and would also slow the progression of such conditions.
In one embodiment of the present invention, a midsole is provided having a body with medial and lateral sides. The height of the lateral side of the body is greater than the height of the medial side, thereby forming a wedge-shaped profile. In one embodiment, the lateral inclination of the midsole is limited to the heel and forefoot portions. Accordingly, the medial and lateral sides of the midsole have a substantially uniform height at the toe and midfoot portions. It is believed that the wedge-shaped profile at the heel and forefoot, but not the midfoot and toe portions, will effectively reduce the peak knee varus torque and hip adductor torque values in early and late stance during walking and running.
In another embodiment, an arch support is provided for supporting the medial side of a wearer""s foot. The arch support is cantilevered to transfer forces from the weight of the body to the lateral side of the shoe and foot, instead of to the medial side of the shoe and foot where it would otherwise be directed. The cantilevered arch support can be mated to the lateral side of the arch support or to the lateral side of the body of the midsole at various locations and by numerous mating techniques.
The cantilevered arch support can be used alone or in combination with the wedge-shaped midsole to reduce the knee varus and hip adductor torques during walking, standing, running, jumping and other weight bearing activities, including athletic endeavors. The cantilevered arch support is at least as effective as a standard arch support in preventing collapse of the arch and in preventing foot pain and deformities. Thus, the cantilevered arch support may be used alone to prevent excessive pronation while simultaneously reducing the knee varus and hip adductor torques. The combination of the cantilevered arch, with both a lateral angulation and flare confined to both the heel and forefoot, should be comfortable about the foot and prevent excessive pronation. At the same time, this combination reduces knee varus and hip adductor torques at both the beginning and the end of the stance. The addition of neutral height from the heel to the forefoot will also contribute to a reduction in knee varus and hip adductor torques.
In another embodiment, the body of the midsole is formed from a compressible top layer and a semi-compressible bottom layer. The bottom layer has a lateral height that is greater than the medial height, while the top layer has a medial height that is greater than the lateral height. The medial and lateral inclinations of the top and bottom layers of the midsoles can be limited to the heel and forefoot portions. The two layers together form a midsole having substantially the same height throughout the body absent any compressible force applied through a wearer""s foot from the weight of the wearer""s body. Due to the different compression properties of the two layers, the midsole achieves a wedge-shaped profile at the heel and forefoot portions upon the application of force from a wearer""s body.
The midsole may also be formed by one or more layers or regions of materials having different compression properties. This design can result in a midsole that has a uniform thickness absent the application of body weight, but which achieves a wedge-shaped profile at the heel and forefoot upon the application of body weight. Alternatively, the one or multiple layered midsole can have a wedge-shaped profile at the heel and forefoot before the application of body weight.
In other aspects of the present invention, a shoe is provided for supporting a wearer""s foot. The shoe includes an outer sole, a midsole disposed on the outer sole, and an upper mated to the midsole along a peripheral portion of the midsole. At least a portion of the lateral side of the midsole has a height that is greater than the height of the medial side of the midsole. The shoe can also include a cantilevered arch support for not only supporting the arch, but for transferring forces from the weight of the body from the medial to the lateral side of the shoe and foot.
The present invention further provides an insole insert for use in a shoe. The insole insert includes a semi-rigid body having a medial side, a lateral side, a forefoot portion, a midfoot portion, a heel portion, and optionally a toe portion. The insole insert has a lateral side height that is greater than the medial side height of the insole insert at the heel and forefoot portions. The insole insert may also include a cantilevered arch support that is attached thereto for transferring forces from the weight of the body to the lateral side of the shoe and foot. The arch support has an upwardly extending portion, which may be adapted to conform to an arch of a wearer""s foot.